File:Kirkes' handbook of physiology (1907) (14789797303).jpg

Identifier: kirkeshandbookof00kirk (find matches)
Title: Kirkes' handbook of physiology
Year: 1907 (1900s)
Authors: Kirkes, William Senhouse, 1823-1864 Greene, Charles Wilson, 1866-1947
Subjects: Physiology
Publisher: New York, W. Wood and company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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e length.They are represented graphically in the diagrams, figures 380 and 396. Reflex Centers of the Medulla. The larger number of the cranialnerves, as we shall presently see, take their origin from the medulla andpons. Some of these nerves have both sensory and motor roots, whileothers are either motor or sensory exclusively. A large percentage of theafferent or sensory impulses that enter the medulla produce reflex effectson the motor nuclei so richly represented in the medulla. The nuclei, orcenters, regulating some of the most important functions of the body are REFLEX CENTERS OF THE .MEDULLA 541 among those in this group. When certain of these centers are interferedwith, death follows. Life may continue when the spinal cord is cut away in successive portionsfrom below upward as high as the point of origin of the phrenic nerves. Inamphibia, the brain has been all removed from above, and the cord removed asfar as the medulla oblongata from below; yet so long as the medulla oblon-
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Fig. 380.—Diagram of Ascending Conduction Paths from the Cord through the Medulla andthe Thalamus to the Cerebral Cortex. (Cunningham.) gata was left intact, respiration and life were maintained. But if the medullaoblongata is wounded, particularly if it is wounded in its central part oppo-site the origin of the vagi, the respiratory movements cease, and the animaldies from asphyxiation. This effect ensues even when all parts of the nervoussystem except the medulla oblongata are left intact. Injury and disease in men are accompanied by the same nerve disturbancesas are exhibited by these experiments on animals. Numerous instances arerecorded in which injury to the medulla oblongata has produced instantaneous 542 . THE NERVOUS SYSTEM death; and, indeed, it is through injury to it, or of the part of the cord con-necting it with the origin of the phrenic nerve, that death is commonly pro-duced in fractures attended by sudden displacement of the upper cervicalvertebrae. The majority of

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